Expression of LFA-1 and Mac-1 in COS-7 cells transiently cotransfected with the wild-type α subunits of Mac-1 or LFA-1, plus the wt, mut-1, or mut-2 β₂ subunit. (A) Fluorescence-activated cell sorter (FACS) histograms for expression of Mac-1 or LFA-1 on COS-7 cells cotransfected as indicated and stained with direct fluorescent conjugates of mAbs against the Mac-1 or LFA-1 α subunits or an isotype-matched control mAb. The thin lines represent background fluorescence with a control antibody, and the thick lines represent the specific fluorescence for LFA-1 or Mac-1. As shown, COS-7 cells transfected with the mut-1 β₂ subunit expressed markedly diminished Mac-1 and LFA-1 compared with cells with the wt β₂, whereas results with the mut-2 β₂ were similar to those for wild type. (B) A graph of the composite data from 4 such experiments, confirming the pronounced reduction in expression of Mac-1 and LFA-1 with the mut-1 β₂ subunit versus wt β₂ (P < .001; n = 5). Error bars indicate SEM. Expression of Mac-1 and LFA-1 with the mut-2 β₂ was equivalent to their expression with wt β₂. RNArecovered from COS-7 cells transiently transfected as for the expression studies for panelsAand B was subjected to Northern analysis as described in “Patients, materials, and methods.” As shown in the autoradiogram in panel C, there was no apparent difference in mRNAabundance among the 3 β₂ mRNAs, confirming that the reduced expression of Mac-1 and LFA-1 with the mut-1 β₂ subunit could not be attributed to reduced transcription. The results shown are for RNA from COS-7 cells transfected with the respective β₂ subunits along with the LFA-1 α subunit and represent 3 similar experiments.